Africanized bees

Africanized bees, also known as Killer bees, are the hybridized honeybees of European stock with an African one. It was first introduced in Brazil in 1950s to increase honey production in the country. However, in 1957, 26 swarms accidentally escaped quarantine and has recently been spread from Brazil to the US.

These bees are very aggressive and hyper defensive in nature and known for attacking humans and animals within the range of 500 metres. It is because of this nature these are colloquially called killer bees, however, they don't attack because of their ferocity. They attack in defense, and attack the perceived threat relentlessly in large numbers. Many deaths are attributed to such attacks.